1. Field of the Invention
The present invention generally relates to a pipette probe and, more particularly, to a pipette probe for use in an automated chemical analyzer, such as, for example, an automated immunoassay analyzer.
2. Description of the Prior Art
Many chemical analysis processes involve adding a reagent to a sample, allowing a chemical reaction to occur, and then analyzing the sample to determine its constitutes. An immunoassay is a well known type of chemical analysis method used to determine the amount of an analyte in a sample such as plasma or urine. It is based on the interaction of antibodies with antigens, and because of the degree of sensitivity for the analyte (either antigen or antibody), an immunoassay can be used to quantitatively determine very low concentrations of drugs, hormones, polypeptides, or other compounds found in a test sample.
Chemical analyses, such as immunoassays, were historically performed by hand by a trained laboratory technician. Recently, many companies have begun producing automated analyzers. Such systems are computerized and may utilize a conveyer chain or belt to convey sample vessels from station to station whereat specific analysis steps are carried out. The sample vessels may be bar coded to instruct the computer of its contents and the specific test which is to be performed on each sample. Based on this information, a precise volume of fluid is pipetted from a reagent container or a sample vessel to a test tube with a syringe mechanism.
Depending on the test to be performed, a multitude of reagents may be required. Some tests may even require a combination of several reagents. One way to prevent cross-contamination between samples, has been to use a separate syringe mechanism for each reagent. This is undesirable since it adds greatly to the mechanical complexity of the analyzer and requires an additional wash step for the pipette tip to reduce the level of contamination between the test samples and unspent reagent supply.
An automated immunoassay system must always generate results which are precise, accurate and independent of one another. These criteria are challenging to achieve since, typically laboratory workloads may demand that an automated system generate as many as 120 test results per hour. Although all instrument processes contribute to the instruments ability to produce such results, perhaps none is more important than the pipetting process. As such, it is imperative that the pipette probe be able to transfer liquids precisely and accurately, with virtually no sample-to-sample carryover. Many automated pipette systems in use today employ a standard stainless steel pipette-probe tip available from, for example, the Hamilton Corporation. However, such commercially available tips are largely unsuitable for immunoassay procedures, since they cause an unacceptably high sample to sample carryover rate which leads to distorted, erroneous immunoassay test results.